The goal of this NIH Bioengineering Research Grant (BRG) in the past funding cycle was to develop a novel morphological and micro-mechanical modeling method for trabecular bone based on digital topological analysis (DTA) of micro-computed tomography (?CT) and micro magnetic resonance images (?MRI) of human trabecular bone samples. Overcoming great technical challenges, we have successfully developed novel individual trabecula segmentation (ITS) based morphological and highly efficient plate-rod (P-R) modeling techniques, which automatically segment trabecular bone microstructure into individual trabecular plates and rods. In this competitive continuation application, we propose to translate our novel bioengineering ITS techniques to whole human bone basic science and computation. We propose to (1) investigate biomechanics of whole body vertebral collapse, which will improve clinical definition of vertebral fractures, and (2) develop computationally efficient, patient-specific P-R models of whole distal tibia and radius bone segments, which will translate our findings to clinical HR-pQCT research, and (3) establish relationships in ITS microstructural measures between the distal tibia/radius and vertebral body. We will the following specific aims in this competitive continuation application: Specific Aim 1: Develop ITS-based P-R finite element models of ?CT images of whole vertebral bodies; validate these highly efficient specimen-specific models in predicting strength by comparison with strength measurements from direct experiments and voxel-based finite element models of vertebral bodies; and determine the roles of trabecular bone density, type, and orientation in whole vertebral collapse using ITS- based P-R model simulations. Specific Aim 2: Develop ITS-based P-R models of HR-pQCT images for whole distal tibia and radius segments and validate these highly efficient patient-specific models in predicting strength by comparison with strength measurements from direct experiments and voxel-based finite element models of distal tibiae or radii. Specific Aim 3: Compare ITS-based measures of whole trabecular bone segments of the distal tibia and radius using HR-pQCT images with those from ?CT of vertebrae from same cadaveric donors. The proposed study will translate the technology of ITS analysis to the study of a novel pathogenesis of osteoporotic vertebral fractures and develop an accurate and highly efficient translational tool for assessing bone strength for clinical research. In addition, we wil also establish microstructural and biomechanical links between the peripheral skeleton (radius and tibia) and the central skeleton (vertebra) such that it will aid mechanistic studies of pathogenesis of osteoporosis and fracture.